Technical Abstract:
Greening of the tuber skin is an undesirable defect. Tubers of 90 Solanum microdontum families represented by 12 individuals each were generated in the winter greenhouse in 2009-2010. These were evaluated in two trials of family bulks after four days of exposure to 200 ft candles of fluorescent white light at room temperature. This light intensity was similar to that measured in local grocery stores, and according to preliminary tests, was known to turn some microdontum tubers very green. A qualitative score of green (G) or white (W) was assigned to each tuber, but notes on shade of green were also made. Tubers of about 80 families were uniformly G or variable, with 10 families noted as mostly W (especially PI 595506 from Argentina). When nine families were selected for replicated follow-up testing on an individual clone basis, the results matched those of the bulk tuber trials, and there was virtually no variation within clone. Two replicates of about 65 G and 65 W individual tubers were selected from a variety of families, and planted in the summer greenhouse to create a new clonal generation of tubers. Those second generation tubers showed a response to illumination which was consistent with that of their mother tubers. In comparison, when 160 named tuberosum cultivars were illuminated in the same way, none from Europe or North America scored W. We are in the process of intermating G and W clones of microdontum to investigate the genetics and physiology of the trait, with a view to eventual breeding of strong greening resistance into cultivars.